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<center><b><font size=-1>COFF: Symbol Table</font></b></center>
<pre>typedef struct {
union {
char <b>e_name</b>[E_SYMNMLEN];
struct {
unsigned long <b>e_zeroes</b>;
unsigned long <b>e_offset</b>;
} e;
} e;
unsigned long <b>e_value</b>;
short <b>e_scnum</b>;
unsigned short <b>e_type</b>;
unsigned char <b>e_sclass</b>;
unsigned char <b>e_numaux</b>;
} <b>SYMENT</b>;</pre>
The symbol table is probably one of the most complex parts of the COFF
object, mostly because there are so many symbol types. The symbol table
has entries for all symbols and meta-symbols, including public, static,
external, section, and debugging symbols.
<dl>
<dt>
<tt>e.e_name</tt> - inlined symbol name</dt>
<dd>
If the symbol's name is eight characters or less, it is stored in this
field. Note that the first character overlaps the
<tt>e_zeroes</tt> field
- by doing so, the <tt>e_zeroes</tt> field can be used to determine if
the symbol name has been inlined. Beware that the name is null terminated
only if it is less than eight characters long, else it is not null terminated.</dd>
<dt>
<tt>e.e.e_zeroes</tt> - flag to tell if name is inlined</dt>
<dd>
If this field is zero, then the symbol name is found by using
<tt>e_offset</tt>
as an offset into <a href="strtab.html">the string table</a>. If it is
nonzero, then the name is in the <tt>e_name</tt> field.</dd>
<dt>
<tt>e.e.e_offset</tt> - offset of name in string table</dt>
<dd>
If <tt>e_zeroes</tt> is zero, this field contains the offset of the symbol
name in <a href="strtab.html">the string table</a>.</dd>
<dt>
<tt>e_value</tt> - the value of the symbol</dt>
<dd>
The value of the symbol. For example, if the symbol represents a function,
this contains the address of the function. The meaning of the value depends
on the type of symbol (<a href="#values">below</a>).</dd>
<dt>
<tt>e_scnum</tt> - section number</dt>
<dd>
The number of the section that this symbol belongs to. The first section
in <a href="scnhdr.html">the section table</a> is section one. In addition,
<tt>e_scnum</tt> may be one of the following values:</dd>
<table>
<tr>
<th>Symbol
<hr noshade size=1></th>
<th>Value
<hr noshade size=1></th>
<th>Meaning
<hr noshade size=1></th>
</tr>
<tr VALIGN=TOP>
<td><tt>N_UNDEF</tt></td>
<td ALIGN=CENTER>0</td>
<td>An undefined (extern) symbol</td>
</tr>
<tr VALIGN=TOP>
<td><tt>N_ABS</tt></td>
<td ALIGN=CENTER>-1</td>
<td>An absolute symbol (<tt>e_value</tt> is a constant, not an address)</td>
</tr>
<tr VALIGN=TOP>
<td><tt>N_DEBUG</tt></td>
<td ALIGN=CENTER>-2</td>
<td>A debugging symbol</td>
</tr>
</table>
<dt>
<tt>e_type</tt> - symbol type</dt>
<dd>
The type of the symbol. This is made up of a base type and a derived type.
For example, "pointer to int" is "pointer to T" and "int".</dd>
<table>
<tr>
<th>Type
<hr noshade size=1></th>
<th>Bits
<hr noshade size=1></th>
<th>Meaning
<hr noshade size=1></th>
</tr>
<tr VALIGN=TOP>
<td><tt>T_NULL</tt></td>
<td><tt>---- 0000</tt></td>
<td>No symbol</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_VOID</tt></td>
<td><tt>---- 0001</tt></td>
<td>void function argument (not used)</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_CHAR</tt></td>
<td><tt>---- 0010</tt></td>
<td>character</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_SHORT</tt></td>
<td><tt>---- 0011</tt></td>
<td>short integer</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_INT</tt></td>
<td><tt>---- 0100</tt></td>
<td>integer</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_LONG</tt></td>
<td><tt>---- 0101</tt></td>
<td>long integer</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_FLOAT</tt></td>
<td><tt>---- 0110</tt></td>
<td>floating point</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_DOUBLE</tt></td>
<td><tt>---- 0111</tt></td>
<td>double precision float</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_STRUCT</tt></td>
<td><tt>---- 1000</tt></td>
<td>structure</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_UNION</tt></td>
<td><tt>---- 1001</tt></td>
<td>union</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_ENUM</tt></td>
<td><tt>---- 1010</tt></td>
<td>enumeration</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_MOE</tt></td>
<td><tt>---- 1011</tt></td>
<td>member of enumeration</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_UCHAR</tt></td>
<td><tt>---- 1100</tt></td>
<td>unsigned character</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_USHORT</tt></td>
<td><tt>---- 1101</tt></td>
<td>unsigned short</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_UINT</tt></td>
<td><tt>---- 1110</tt></td>
<td>unsigned integer</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_ULONG</tt></td>
<td><tt>---- 1111</tt></td>
<td>unsigned long</td>
</tr>
<tr VALIGN=TOP>
<td><tt>T_LNGDBL</tt></td>
<td><tt>---1 0000</tt></td>
<td>long double (special case bit pattern)</td>
</tr>
<tr VALIGN=TOP>
<td><tt>DT_NON</tt></td>
<td><tt>--00 ----</tt></td>
<td>No derived type</td>
</tr>
<tr VALIGN=TOP>
<td><tt>DT_PTR</tt></td>
<td><tt>--01 ----</tt></td>
<td>pointer to T</td>
</tr>
<tr VALIGN=TOP>
<td><tt>DT_FCN</tt></td>
<td><tt>--10 ----</tt></td>
<td>function returning T</td>
</tr>
<tr VALIGN=TOP>
<td><tt>DT_ARY</tt></td>
<td><tt>--11 ----</tt></td>
<td>array of T</td>
</tr>
</table>
<p>The <tt>BTYPE(x)</tt> macro extracts the base type from <tt>e_type</tt>.
Note that all <tt>DT_*</tt> must be shifted by <tt>N_BTSHIFT</tt> to get
actual values, as in:
<pre>e_type = <i>base</i> + <i>derived</i> << N_BTSHIFT;</pre>
There are also macros <tt>ISPTR</tt>, <tt>ISFCN</tt>, and <tt>ISARY</tt>
that test the upper bits for the derived type.
<dt>
<tt>e_sclass</tt> - storage class</dt>
<dd>
This tells where and what the symbol represents.</dd>
<table>
<tr>
<th>Class
<hr noshade size=1></th>
<th>Value
<hr noshade size=1></th>
<th>Meaning
<hr noshade size=1></th>
</tr>
<tr VALIGN=TOP>
<td><tt>C_NULL</tt></td>
<td ALIGN=CENTER><tt>0</tt></td>
<td>No entry</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_AUTO</tt></td>
<td ALIGN=CENTER><tt>1</tt></td>
<td>Automatic variable</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_EXT</tt></td>
<td ALIGN=CENTER><tt>2</tt></td>
<td>External (public) symbol - this covers globals and externs</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_STAT</tt></td>
<td ALIGN=CENTER><tt>3</tt></td>
<td>static (private) symbol</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_REG</tt></td>
<td ALIGN=CENTER><tt>4</tt></td>
<td>register variable</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_EXTDEF</tt></td>
<td ALIGN=CENTER><tt>5</tt></td>
<td>External definition</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_LABEL</tt></td>
<td ALIGN=CENTER><tt>6</tt></td>
<td>label</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_ULABEL</tt></td>
<td ALIGN=CENTER><tt>7</tt></td>
<td>undefined label</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_MOS</tt></td>
<td ALIGN=CENTER><tt>8</tt></td>
<td>member of structure</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_ARG</tt></td>
<td ALIGN=CENTER><tt>9</tt></td>
<td>function argument</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_STRTAG</tt></td>
<td ALIGN=CENTER><tt>10</tt></td>
<td>structure tag</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_MOU</tt></td>
<td ALIGN=CENTER><tt>11</tt></td>
<td>member of union</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_UNTAG</tt></td>
<td ALIGN=CENTER><tt>12</tt></td>
<td>union tag</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_TPDEF</tt></td>
<td ALIGN=CENTER><tt>13</tt></td>
<td>type definition</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_USTATIC</tt></td>
<td ALIGN=CENTER><tt>14</tt></td>
<td>undefined static</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_ENTAG</tt></td>
<td ALIGN=CENTER><tt>15</tt></td>
<td>enumaration tag</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_MOE</tt></td>
<td ALIGN=CENTER><tt>16</tt></td>
<td>member of enumeration</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_REGPARM</tt></td>
<td ALIGN=CENTER><tt>17</tt></td>
<td>register parameter</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_FIELD</tt></td>
<td ALIGN=CENTER><tt>18</tt></td>
<td>bit field</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_AUTOARG</tt></td>
<td ALIGN=CENTER><tt>19</tt></td>
<td>auto argument</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_LASTENT</tt></td>
<td ALIGN=CENTER><tt>20</tt></td>
<td>dummy entry (end of block)</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_BLOCK</tt></td>
<td ALIGN=CENTER><tt>100</tt></td>
<td>".bb" or ".eb" - beginning or end of block</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_FCN</tt></td>
<td ALIGN=CENTER><tt>101</tt></td>
<td>".bf" or ".ef" - beginning or end of function</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_EOS</tt></td>
<td ALIGN=CENTER><tt>102</tt></td>
<td>end of structure</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_FILE</tt></td>
<td ALIGN=CENTER><tt>103</tt></td>
<td>file name</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_LINE</tt></td>
<td ALIGN=CENTER><tt>104</tt></td>
<td>line number, reformatted as symbol</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_ALIAS</tt></td>
<td ALIGN=CENTER><tt>105</tt></td>
<td>duplicate tag</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_HIDDEN</tt></td>
<td ALIGN=CENTER><tt>106</tt></td>
<td>ext symbol in dmert public lib</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_EFCN</tt></td>
<td ALIGN=CENTER><tt>255</tt></td>
<td>physical end of function</td>
</tr>
</table>
<dt>
<tt>e_numaux</tt> - number of auxiliary entries</dt>
<dd>
Each symbol is allowed to have additional data that follows it in the symbol
table. This field tells how many equivalent SYMENTs are used for aux entries.
For most symbols, this is zero. A value of one allows up to SYMESZ bytes
of auxiliary information for that symbol. A non-exhaustive list of auxiliary
entries follows, based on the storage class (<tt>e_sclass</tt>) or type
(<tt>e_type</tt>) of the symbol.</dd>
</dl>
<h2>
Auxiliary Entries</h2>
<dl>
<dt>
<b><tt>DT_ARY</tt></b></dt>
<dt>
<tt>.x_sym.x_misc.x_lnsz.x_size</tt></dt>
<dd>
size in bytes (size*count)</dd>
<dt>
<b><tt>T_STRUCT</tt></b></dt>
<dt>
<b><tt>T_UNION</tt></b></dt>
<dt>
<b><tt>T_ENUM</tt></b></dt>
<dt>
<tt>.x_sym.x_tagndx</tt></dt>
<dd>
syment index for list of tags (will point to <tt>C_STRTAG</tt>, <tt>C_UNTAG</tt>,
or <tt>C_ENTAG</tt>)</dd>
<dt>
<tt>.x_sym.x_misc.x_lnsz.x_size</tt></dt>
<dd>
size in bytes (size*count)</dd>
<dt>
<b><tt>T_NULL | C_STAT</tt></b> - section symbols (like <tt>.text</tt>)</dt>
<dt>
<tt>.x_scn.x_scnlen</tt></dt>
<dd>
section length (bytes)</dd>
<dt>
<tt>.x_scn.x_nreloc</tt></dt>
<dd>
number of relocation entries (ushort)</dd>
<dt>
<tt>.x_scn.x_nlinno</tt></dt>
<dd>
number of line numbers (ushort)</dd>
<dt>
<b><tt>C_STRTAG</tt></b> - will be followed by <tt>C_MOS</tt>'s and <tt>C_EOS</tt></dt>
<dt>
<b><tt>C_UNTAG</tt></b> - will be followed by <tt>C_MOU</tt>'s and <tt>C_EOS</tt></dt>
<dt>
<b><tt>C_ENTAG</tt></b> - will be followed by <tt>C_MOE</tt>'s and <tt>C_EOS</tt></dt>
<dt>
<tt>.x_sym.x_x_misc.x_lnsz.x_size</tt></dt>
<dd>
The size of the struct/union/enum</dd>
<dt>
<tt>.x_sym.x_fcnary.x_fcn.x_endndx</tt></dt>
<dd>
The symbol index after our list.</dd>
<dt>
<b><tt>C_EOS</tt></b></dt>
<dt>
<tt>.x_sym.x_misc.x_lnsz.x_size</tt></dt>
<dd>
the size of the struct/union/enum</dd>
<dt>
<tt>.x_sym.x_tagndx</tt></dt>
<dd>
The symbol index of the start of our list.</dd>
<dt>
<b><tt>C_FIELD</tt></b></dt>
<dt>
<tt>.x_sym.x_x_misc.x_lnsz.x_size</tt></dt>
<dd>
the number of bits</dd>
<dt>
<b><tt>C_BLOCK</tt></b></dt>
<dt>
<tt>.x_sym.x_misc.x_lnsz.x_lnno</tt></dt>
<dd>
starting line number</dd>
<dt>
<tt>.x_sym.x_fcnary.x_fcn.x_endndx</tt></dt>
<dd>
The symbol index after our block (if <tt>.bb</tt>)</dd>
<dt>
<b><tt>C_FCN</tt></b></dt>
<dt>
<tt>.x_sym.x_misc.x_lnsz.x_lnno</tt></dt>
<dd>
starting line number</dd>
<dt>
<tt>.x_sym.x_misc.x_lnsz.x_size</tt></dt>
<dd>
size in bytes</dd>
<dt>
<b><tt>C_FILE</tt></b></dt>
<dt>
<tt>.x_file.x_fname</tt></dt>
<dt>
<tt>.x_file.x_n.x_zeroes</tt></dt>
<dt>
<tt>.x_file.x_n.x_offset</tt></dt>
<dd>
These three specify the file name, just like the three fields used to specify
the symbol name.</dd>
</dl>
<h2>
<a NAME="values"></a>Meanings of the Values</h2>
<table>
<tr>
<th>SClass
<hr noshade size=1></th>
<th>Meaning of the Value
<hr noshade size=1></th>
</tr>
<tr VALIGN=TOP>
<td><tt>C_AUTO</tt>
<br><tt>C_ARG</tt></td>
<td>Address of the variable, relative to <tt>%ebp</tt></td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_EXT</tt>
<br><tt>C_STAT</tt>
<br><tt>others</tt></td>
<td>The address of the symbol</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_REG</tt></td>
<td>The register number assigned to this variable</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_MOS</tt></td>
<td>Offset of the member from the beginning of the structure</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_MOE</tt></td>
<td>The value of this enum member</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_FIELD</tt></td>
<td>The mask for this field</td>
</tr>
<tr VALIGN=TOP>
<td><tt>C_EOS</tt></td>
<td>size of struct/union/enum</td>
</tr>
</table>
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